1. Technical Field
The present invention relates to stators for rotating electric machines that are used in, for example, motor vehicles as electric motors and electric generators, and to methods of manufacturing the stators.
2. Description of Related Art
There are known, for example from Japanese Patents No. 3738733 and No. 4646038 (to be respectively referred to as Patent Documents 1 and 2 hereinafter), stators for rotating electric machines which include a hollow cylindrical stator core and a stator coil formed of a plurality of electric conductor segments mounted on the stator core. Specifically, the stator core has a plurality of slots formed therein; the slots are spaced from one another in the circumferential direction of the stator core. The electric conductor segments are partially received in the slots of the stator core so that they are radially aligned with one another in the slots and have respective protruding portions that protrude outside of the slots on an axial side of the stator core. All the protruding portions of the electric conductor segments together make up a coil end of the stator coil. Moreover, corresponding pairs of the protruding portions of the electric conductor segments are joined by, for example, welding. In addition, each of the electric conductor segments has an insulating coat covering its outer surface so that the electric conductor segments are electrically insulated from each other in the slots of the stator core.
Further, in the stator disclosed in Patent Document 1, each of the protruding portions of the electric conductor segments intersects at least one of the other protruding portions which is radially adjacent to the protruding portion. Further, each of the protruding portions of the electric conductor segments has an indentation (or a recess) formed in a side face thereof radially facing the at least one other protruding portion at the intersection therebetween. Consequently, with the indentations formed in the side faces of the protruding portions of the electric conductor segments, a sufficient clearance can be secured between each intersecting pair of the protruding portions of the electric conductor segments, thereby improving both electrical insulation between the protruding portions and cooling of the protruding portions via cooling air.
However, according to the disclosure of Patent Document 1, the indentations are formed in the side faces of the protruding portions of the electric conductor segments by pressing. Consequently, the thickness of the insulating coats covering the outer surfaces of the electric conductor segments may be reduced at the indentations, thereby lowering the insulating performance of the insulating coats at the indentations.
On other hand, in the stator disclosed in Patent Document 2, those portions of the electric conductor segments which are received in the slots of the stator core have a rectangular cross-sectional shape. Further, the thickness of the insulating coats covering those in-slot portions of the electric conductor segments is set to be smaller than the thickness of the insulating coats covering those portions of the electric conductor segments which protrude outside of the slots of the stator. Consequently, with the smaller thickness of the insulating coats covering the in-slot portions of the electric conductor segments, it is possible to more effectively transmit heat generated by the in-slot portions of the electric conductor segments to the stator core. At the same time, with the larger thickness of the insulating coats covering the protruding portions of the electric conductor segments, it is possible to secure electric insulation between the protruding portions of the electric conductor segments.
However, according to the disclosure of Patent Document 2, it may be difficult to reliably ensure electrical insulation between the in-slot portions of the electric conductor segments due to the smaller thickness of the insulating coats covering the in-slot portions.